Abstract

Type 1 diabetes (T1D) is a chronic disease characterized by an autoimmune-mediated destruction of insulin-producing pancreatic β cells. Environmental factors such as viruses play an important role in the onset of T1D and interact with predisposing genes. Recent data suggest that viral infection of human islets leads to a decrease in insulin production rather than β cell death, suggesting loss of β cell identity. We undertook this study to examine whether viral infection could induce human β cell dedifferentiation. Using the functional human β cell line EndoC-βH1, we demonstrate that polyinosinic-polycytidylic acid (PolyI:C), a synthetic double-stranded RNA that mimics a byproduct of viral replication, induces a decrease in β cell–specific gene expression. In parallel with this loss, the expression of progenitor-like genes such as SOX9 was activated following PolyI:C treatment or enteroviral infection. SOX9 was induced by the NF-κB pathway and also in a paracrine non–cell-autonomous fashion through the secretion of IFN-α. Lastly, we identified SOX9 targets in human β cells as potentially new markers of dedifferentiation in T1D. These findings reveal that inflammatory signaling has clear implications in human β cell dedifferentiation.

Figure 7

(A) Venn diagram with genes upregulated (>2-fold) in EndoC-βH1 cells treated with PolyI:C and following ectopic expression of SOX9/VP16-SOX9ΔTAD. Genes upregulated by both PolyI:C and SOX9/VP16-SOX9ΔTAD are shown in red. (B) EndoC-βH1 cells were transfected with MCS-ires-GFP, SOX9WT-ires-GFP, VP16-ires-GFP, or VP16-SOX9ΔTAD-ires-GFP plasmid. GFP+ cells were sorted by FACS 48 hours later and RNA was prepared for RT-qPCR analyses (n = 3). (C–E) EndoC-βH1 cells were transfected with control nontarget siRNA (siCTRL) or siRNA targeting SOX9 (siSOX9). They were next either mock transfected or transfected with PolyI:C. Twenty-four hours later, proteins were prepared for Western blot analyses (n = 3) (C and D) and RNA for RT-qPCR (n = 3) (E). Data from RT-qPCR and Western blot represent the mean ± SD of 3 independent experiments. *P < 0.05; **P < 0.01; and ***P < 0.001 relative to control by Student’s t test or ANOVA with Bonferroni’s correction for multiple comparisons. ns, not significant.